1. Field of the Invention
The present invention relates to a method of simulating tire tread noise and a simulator therefor. More specifically, the present invention relates to a method of simulating tire tread noise and a simulator of tire tread noise whereby tire noise with high fidelity can be generated.
2. Description of the Related Art
The method of simulating tire tread noise on which the present invention is based is disclosed in U.S. Pat. Nos. 4,727,501 and 4,788,651. In this method, a tread surface is represented as a large number of matrix elements on a coordinate system in order to distinguish between load-supporting portions (i.e. lugs) and grooves of the tread, to thereby determine a contour of a front edge of a contact portion (footprint) of the tread which comes into contact with the road surface, or a contour of a rear edge of this contact portion, in accordance with an equation. Then, the waveforms of sound generated from each of the matrix elements, which are sound sources, are determined and the waveforms of sound are integrated over the contours of the front edge or the rear edge of the footprint. Next the so-integrated value is further integrated along the direction of the circumference of the tire, and audible sound is generated on the basis of the integrated value, thereby simulating tire tread noise.
When the load-supporting portion of the tread comes into contact with the road surface and when the load-supporting portion which has contacted the road surface separates from the road surface, the contacting portion of the load-supporting portion which comes into contact with the road surface and another portion of the load-supporting portion which separates from the road surface are sources of vibration, and cause the tread rubber to vibrate. The vibration of the tread rubber is transmitted to the side walls of the tire and thus, tire tread noise is generated. This is understood by inventors of the present invention. However, in the conventional simulating method, the waveform of sound has been integrated along either the contour of the front edge or the contour of the rear edge of the footprint, by assuming that the entire surface of the load-supporting portion will be a source of sound, without specifying the actual portions thereof which constitute the sound source. As a result, there exists a problem that it is not possible to simulate the sound with high fidelity by such a technique since it is not possible to integrate sound generated from the actual source of sound, and also not possible to integrate sound, considering the phase of the sound.